if (/MSIE (\d+\.\d+);/.test(navigator.userAgent)) 
{ //test for MSIE x.x;
    var ieversion = new Number(RegExp.$1) // capture x.x portion and store as a number
    if (ieversion < 7)
    {
        alert("We notice you are using an older version of Internet Explorer.  Please upgrade to the latest version for the best experience!");
        //window.location = "http://www.microsoft.com/windows/downloads/ie/getitnow.mspx";
     }
}